Field of the Invention
The present invention relates to an internal combustion engine, a control method thereof, and a controller therefor.
Background Art
There are some known internal combustion engines that can run on a gasoline/alcohol mixed fuel. For example, Patent Literature 1 (Japanese Patent Laid-Open No. 2009-281216) discloses an internal combustion engine that performs a control to increase the fuel injection amount to increase the engine torque during high load operation and, in the fuel injection amount increasing control, makes a correction to decrease the increment of the fuel injection amount as the alcohol concentration of the fuel increases. Such a correction can prevent occurrence of engine torque variations due to variations of alcohol concentration of the fuel during high load operation.
Other prior art includes Japanese Patent Laid-Open No. 10-122013 and Japanese Patent Laid-Open No. 5-106498.
With an internal combustion engine that runs on a gasoline/alcohol mixed fuel, unburned alcohol or water produced by combustion may react with calcium in oil on the wall of the bore of the combustion chamber to form calcium carbonate, calcium sulfate or other deposits. Such deposits increase the sliding friction between the wall of the bore and the piston ring. As a result, the smoothness of the movement of the piston is likely to decrease.